Crossbar/hub arrangement for multimedia network

ABSTRACT

A home network architecture has an internal digital network interconnecting devices in the home. Entertainment services are introduced into the network through network interface units that are coupled to an external network and to internal network. The network interface units are selectively directly connected by a direct circuit crossbar to set-top electronics so that video data, for example, may be directly provided from a network interface unit to the set-top electronics without jitter. A passive hub, which does not have packet routing capability, is then used to provide signal regeneration and re-transmission of other data over the network.

RELATED APPLICATIONS

This patent application is related to U.S. application Ser. No.08/561,758, filed on Nov.22,1995, entitled HOME MULTIMEDIA NETWORKARCHITECTURE; U.S. application Ser. No. 08/561,757, filed onNov.22,1995, entitled SET-TOP ELECTRONICS AND NETWORK INTERFACE UNITARRANGEMENT; U.S. application Ser. No. 08/561,535, filed on , Nov. 22,1995, entitled METHOD AND APPARATUS FOR RECOVERING DATA STREAM CLOCK.

1. Field of the Invention

The present invention relates to multimedia digital networks, and moreparticularly, to the hub of a network that receives and re-transmitsdata over the network to and from end units or terminals connected tothe network.

2. Background of the Invention

The rapid gains in digital technology and telecommunications haveincreased the desirability of having a network in the home tointerconnect a multitude of products in the home with each other and tothe outside world. The range of available outside services includesinteractive services, cable video and audio services, satellitenetworks, telephone company services, video on demand, and other typesof information services. However, penetration of the personal computerinto homes in the United States is approximately 33% and only growingslowly, although governments desire more extensive penetration toencourage "telecommuting" and reduce road traffic and pollution. Furtherpenetration of computers in the home will originate from the purchase ofconsumer entertainment and informational products containing an embeddedcomputer and operating system hidden by an opaque user interface. Such aproduct is a conventional set-top box.

Set-top boxes are multi-media computers that augment the use oftelevisions. A conventional set-top box has an external networkinterface module that connects the set-top box to the external networkand data provider. The network interface module has to perform a numberof sophisticated functions, such as interfacing to a specific externalnetwork, tuning, demodulation, error correcting, video descrambling,recovery of MPEG clock, and encryption and decryption specific to theexternal network. Consequently, the network interface module is arelatively expensive component of Set-top boxes. This expense would benecessary even when a single television is present in the house.However, most homes contain multiple televisions, and providing eachwith its own set-top box and associated network interface module is aduplication of expensive components.

The conventional hub in a network has a signal regeneration functionsuch that a signal may be transmitted a maximum distance in the networkfrom a device to a hub, and another maximum distance again from the hubto another device. A complex hub in a network has a store and forward orpacket routing scheme that examines the addresses of data packets asthey are received by the hub, and performs a switching function toproperly route the data packets to their intended destination. Thisfunctionality comes at a high price, however, so that the costs of ahome network with such a hub may be prohibitively high for the typicalhomeowner, who will then shy away from installing a home network.

SUMMARY OF THE INVENTION

The above described and other problems are overcome by the presentinvention which provides a method and apparatus for connecting terminalsto a network. In certain embodiments of the invention, a passive hub anddirect circuit crossbar arrangement are provided. The passive hub, whichdoes not have any packet routing circuitry, merely regenerates signalsit receives and transmits the signals over the network. A direct circuitcrossbar provides a selectively switchable direct circuit for twoterminals on the network, effectively bypassing the hub and the network.

The establishment of a direct circuit may be used, for example, betweena network interface unit to transmit video data directly to set-topelectronics. This provides the advantages of separating the networkinterface unit from the set-top electronics, i.e., no duplication of thenetwork interface units for a particular service at each set-topelectronics, ability to select among competing service providers, etc.These advantages are gained without the loss, however, of picturequality which might otherwise occur if the direct circuit through thecrossbar were not available, as an inexpensive home network based onEthernet, for example, would likely introduce unacceptable jitter to thesignal. The direct circuit crossbar provides the direct circuit betweenthe network interface unit and the set-top electronics as if they werephysically located in proximity to one another and connected by a bus,as in conventional set-top boxes.

When other data is sent to a directly connected network interface unit,but is not intended for the directly connected set-top electronics, thisdata may be re-routed by the set-top electronics onto the network as awhole through the hub. This avoids the need for a complex switchingarrangement to accomplish this function of introducing data into thenetwork in addition to the direct transmission of the video data to theset-top electronics.

The foregoing and other features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a home network constructed inaccordance with an exemplary embodiment of the present invention.

FIG. 2 is a depiction of an exemplary installation of the home networkof the present invention within a home.

FIG. 3 is a logical diagram of the home network of FIG. 1.

FIG. 4 is a schematic depiction of a network interface unit and aset-top electronics unit constructed in accordance with preferredembodiments of the present Invention.

FIG. 5 is a block diagram of a network interface of the set-topelectronics constructed in accordance with an exemplary embodiment ofthe present invention.

FIG. 6 is a block diagram of the network interface of the networkinterface unit constructed in accordance with an embodiment of thepresent invention.

FIG. 7 is a block diagram of a hub and direct circuit crossbar,constructed in accordance with an embodiment of the present invention,coupled to a network interface unit and a set-top electronics unit.

FIG. 8 is a logical diagram of an exemplary user interface for the homenetwork of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic depiction of a home multimedia network 10constructed in accordance with an embodiment of the present invention.This embodiment is exemplary only, however, as the network 10 may beconfigured in any of a number of different ways within the scope of theinvention, and include different devices coupled to the network 10.Additionally, the invention is not limited to networks located in homes,but is applicable to networks installed in other types of structures,such as offices, apartment buildings, etc. For purposes of illustration,however, the exemplary embodiment will be described in the context of ahome installation.

The network 10 is a digital network that provides connectivity ofdifferent types of equipment to the world outside the home. Thisequipment can be, for example, analog television 12, digital television14, digital VCR 16, digital camcorder 18, personal computers 20, audioequipment 22, printers 24, facsimile machines 26, and telephones 28,among others. In addition to connecting this equipment to the outsideworld, the network 10 also connects the digital video, digital audio,computer and telephone equipment together internally in the home. Thisunifies communication and control within the home, making the full powerof the external network connections or internal data sources availableto any terminal on the network 10.

Communication with the outside world is performed through a number ofseparate network interface units (NIU's) 32 and may be combinedphysically in an entrance unit 30, with each network interface unit 32permitting a connection between a different external network and thehome network 10. The different external networks may carry differenttypes of signals. These may be, for example, broadcast signals (digitalor mixed analog/digital) carried on hybrid fiber coax or cable. Othertypes of signals are ISDN, broadcast/digital satellite service, FTTC,FTTH, ADSL, and others. At least the following data types may becarried: compressed video, compressed audio, compressed internet WWWgraphics and data, internet e-mail and other data, computer file dataand control message data.

Logically all terminals in the home network 10 receive equal access tothe network interface units 32 and a user would be unaware of thephysical sighting of them. The number of network interface units 32 thatare required is determined by the number of streams required per home,e.g. the number of different program channels (i.e., video, audio, andother) required simultaneously, not by the number of terminal units in ahome.

In certain preferred embodiments, cable or antenna television isretained unmodified with distribution by regular in-home coax (plain oldtelevision, or POTV). POTS (plain old telephone service) is also carriedon the in-home digital network 10.

The digital signals are distributed throughout the home over an internalnetwork 34. In certain preferred embodiments, the internal network 34 isessentially Ethernet of type 10base-T or 100base-T twisted pair but aspecial switch hub is employed to make the network scalable to anynumber of terminal units each able to receive high bit-rate video.

The home network 10 connects those computers, or products with embeddedcomputers, that can support the networking bandwidth, protocols,routing, buffering and addressing. Other high bandwidth products that donot support this complex functionality must attach to such a host uniteither directly or via a local peripheral network to achieveinteroperability. Examples of computers or products with embeddedcomputers located on the home network 10, functioning as end userdevices, include: the network interface units's I/O computers performingexternal network to home network conversion and conditioning; computers,such as the set-top electronics (STE); PC's; workstations; high endprinters; and special computers providing gateway/control functions.Other end user devices that can be coupled to the network 10 includevideo products: digital compressed (MPEG) and uncompressed videoequipment; digital video camcorder products; digital video taperecording products and digital tv display products and analog tv displayand recording products. Audio products that can be coupled to thenetwork 10 include: digital compressed (MPEG) and uncompressed audioequipment; HIFI stereo; digital audio tape recording products. Othertypes of products that can connect to the network 10 are data products,such as printers and other peripherals. Still further products that canbe controlled through the network 10 include home automation andappliances: central heating/AC, security controller, microwave oven andother kitchen equipment, lighting, sprinkler and other power control.

Certain embodiments of the home network 10 include one or more localperipheral networks 15 that provide local connection for future veryhigh bit rate, motion-JPEG or I-frame-only-MPEG video devices, audiodevices, printers and such peripherals. These devices need continuouslocal digital connection at a high bandwidth, where the data transfer iscontinuous from, for example, digital camera to digital VCR.Accommodating such devices directly on the internal network 34 wouldrequire greater network bandwidth over the entire network 34 thannormally needed. Instead, the local peripheral network 15 is normallyconnected by gateway to the internal network 34 for interoperability.However, in certain other embodiments of the invention, the home network10 is provided with hardware and software that accommodates the highspeed devices so that a local peripheral network 15 is not necessary.

A home automation network 17 is provided for home automation. This homeautomation network 17 may run on the power line or other low bit ratenetwork for controlling appliances, home security systems, lighting,etc. This spur originates from a control computer 20 located within thehome.

An exemplary model of the installation of the home network 10 of thepresent invention within a house 36 is depicted in FIG. 2. The homenetwork 10 is a long range backbone capable of up to 100 m cable runs,for example, from a switched hub 38 that forms part of the internalnetwork 34. In the exemplary installation depicted in FIG. 2, theentrance unit 30 with its multiple network interface units 32 arelocated in a utility area of the house, along with the switched hub 38.

Twisted pair cable is run to each room of the house 36 and terminates ata wall socket. Cat-5 twisted pair (for 100 Mbits/s), for example, may beused when doing an installation, as the majority of the cost is labor.For temporary retro-installation, twisted pair cable is small enoughthat it may be customer fitted under a carpet edge. A user in the homewill connect a computer product in a room by plugging the Ethernet portof the computer product to the Ethernet wall socket.

In the embodiment of FIG. 2, the hub 38 is depicted as a separatedevice, but in other embodiments the hub 38 is integrated into one ormore of the network interface units 32. The hub 38 provides theconnectivity to all areas of the house and the one or more networkinterface units 32. Upgrading, expanding both the aggregate bandwidthand connectivity of the internal network 34, is accomplished byadditional plugging or changing to a larger hub. The hub will bediscussed in more detail later.

The present invention, as shown in FIGS. 1 and 2, separates thefunctionality of the network interface units 32 from the set-topelectronics 40. Conventionally, a set-top box contains a networkinterface unit whose components are internally connected by a bus to theset-top electronics components. By contrast, however, the presentinvention provides a separation of the network interface units 32 andthe set-top electronics 40, with the internal network 34 interposedtherebetween. This arrangement permits multiple set-top electronics tobe distributed throughout the home 36 less expensively, since theelectronics of a network interface unit do not have to be duplicated foreach set-top electronics. Additionally, having separate networkinterface units 32 coupled to different external networks and to acommon internal network 34 frees the homeowner from being forced toreceive all programing from a single source, such as the telephone orcable company. The separation also allows the homeowner to add, drop orchange services simply by changing one of the network interface units32, without the need for replacing all of the set-top electronics 40throughout the home 36.

In certain embodiments, a "master" set-top box is provided with multiplenetwork interface units. However, this embodiment is logically the sameas described above, as the network interface units are connected in thisembodiment to the internal network, and not by a bus to the set-topelectronics.

FIG. 3 is a logical view of the home network 10 of the presentinvention. As apparent from the diagram, the multi-port switched hub 38forms the center of the network connections. In certain embodiments, inwhich inter-packet jitter is adequately controlled, a traditional,commercially available packet switched hub is employed. In otherpreferred embodiments, such as that depicted in FIG. 3, the switched hub38 is a combination of networked ports and ports that are direct(circuit) switched for the duration of a session. The direct connectedports (and systems) can be phase locked via the network (coded) clock.To provide this functionality, the switched hub 38 therefore comprises arelatively simple and inexpensive hub 42 and a direct circuit crossbar44. The hub 42, in certain preferred embodiments, may be a commerciallyavailable device, such as Am79C981 manufactured by Advanced MicroDevices, of Sunnyvale, Calif. Details of the direct circuit crossbar 44will be described later with respect to FIG. 7.

A star topology as defined by Ethernet 10/100base-T is used inconjunction with the switching hub 38. The switching hub 38 provides fanout to most rooms in the house 36. The maximum system bandwidth is amultiple of the wire bit rate ((bit rate×number of ports)/2), forexample, 20 ports and 100 Mbits/s bit rate =1 Gb/s aggregate maximumbandwidth.

The switched hub 38 enables special treatment for the heavily asymmetrictraffic, e.g., compressed digital video and internet data by directlyrouting these cases from transmitter to receiver. This traffic is thusseparated from the internal network 34 and allows an overall aggregatebandwidth to be limited only by the expandability of the hub 38,although it will remain limited by the 10 Mbits/s per branch. Use of100base-T technology instead of 10base-T technology will uprate thenetwork if required.

The switching hub's direct synchronous (Manchester or block encoded)connections are used primarily for the transmission of MPEG video wherea continuous, high bit rate, long duration connection is required. Highbit rate video in compressed form can be as high as 8 Mbits/sec and isneeded for live video and high action movies and sports. Low bit-ratevideo is 1.5 Mbits/sec. According to the present invention, MPEG digitalvideo is retained throughout the network 10. Conversion to real videotakes place only at the display device (e.g., television 12) or theset-top electronics 40.

Two separate direct circuits are depicted as examples in FIG. 3. Forexample, the network interface unit 32 that is coupled to an ISDNnetwork is directly connected through the direct circuit crossbar 44 tothe personal computer 20 of the local peripheral network 15. Another,separate direct circuit is provided by the direct circuit crossbar 44between a different network interface unit 32 (coupled to hybrid fibercoax, for example) and the set-top electronics 40 coupled to thetelevision 12. Those devices that are not directly connected through thedirect circuit crossbar 44 remain attached to the hub 42 and are thusnetworked.

With respect to the switching hub architecture, where a directpoint-to-point path is configured, all data traversing this path isprovided directly to the end point terminal of the path, even dataintended for one or more other terminals. Thus, in certain preferredembodiments, a rule is followed that data multiplexed with the high ratedata (typically messaging) must be issued to networked terminals by theend point of the direct path returning such packets to the hub 38. Forexample, messages sent over the ISDN network that are not intended for adevice on the local peripheral network 15 will be returned by the localperipheral network host 20 to the hub 38 for distribution. This rulesaves the expense and complication of having a packet router typeswitched hub, with the demultiplexing distributed at the end point(s)rather than centrally, and works well for asymmetric data flow and localdestination, i.e., not subject to layers of switches.

An advantage of directly switched paths is that potential delays inobtaining access to the network 34 (and possibly upsetting the delicateclock reference timing carried in the MPEG stream) are avoidedaltogether.

The hub 38, in certain preferred embodiments, is required to be"full-duplex aware" meaning that a directly routed path connects only atransmitter terminal "up" path only to a receive terminal "down" path.By contrast, the path down to the transmitter and path up to thereceiver are not affected by the direct circuit and would normally beattached to the network, i.e., attached to all the remaining terminalpaths connected together.

Specific routing occurs in response to user service requests. Messagesare picked up by the hub control and any direct routing changesimplemented. Devices not switched from the network connect and norouting is required.

The MPEG clock recovery is performed at the network interface units 32,as described later. With the MPEG clock recovery at the networkinterface units 32, and the establishment of a direct circuit to thehome network destination, jitter in the signal received at thedestination (such as the television 12) is substantially eliminated.Direct circuit capability works well for the heavily asymmetric point topoint traffic expected in the entertainment (video) home scenario.

For analog only services, e.g., transitional cable TV, this is notconsidered part of the digital network. For mixed digital/analogservices such as hybrid fiber coax (HFC) and newer forms of mixed cableTV, this is considered a transitional state and dealt with as atemporary add-on to the all digital system of the present invention. Thesignal from the hybrid fiber coax is provided directly to a set-topelectronics 40 or to a network interface unit 32/set-top electronics 40combination. Two ports are required to connect to the home network 10,one for the network interface unit 32 and one for the set-topelectronics 40. A bypass is provided in certain preferred embodiments tolink the analog signals across to the audio/video circuits of theset-top electronics 40.

The home network 10 is controlled via hand held commander or computerkeyboard to software running at the local terminals, such as thepersonal computers 20, or set-top electronics 40. Control software localto each home terminal manages source availability, source selection,path management by communication with the network interface units 32 andexternal gateways. The external network protocols are buffered in thenetwork interface units 32 to provide a standard interface to theterminals on the home network 10. FIG. 8 depicts one an example of auser interface. In this embodiment, the home network 10 is transparentand the user is only aware of it indirectly from the number of connectedservices.

FIG. 4 is a block diagram depicting a single network interface unit 32coupled by the internal network 34 to a single set-top electronics unit40. The remaining portions of the home network 10, including theswitching hub 38, are not shown in FIG. 4 for purposes of illustrationand explanation.

The network interface unit 32 has one or more network interface modules50 that interface the network interface unit 32 to a particular externalnetwork. In the example of FIG. 4, the network interface module 50provides an interface to an external network that carries MPEG videodata. The MPEG video data is provided to an internal network interfacedevice 52 that prepares the data for transport over the internal network34. In certain preferred embodiments, the internal network 34 is anEthernet network, so that the internal network interface device 52 is anEthernet interface device.

The architecture of the present invention assumes that for some networksa first stage demultiplexing at the network interface unit 32 isnecessary to stay within a definable bandwidth limit (one stream) ratherthan an arbitrary bandwidth set by the construction of the incomingstream (multiple streams). Making the assumption that MPEG-2 video isbeing used, there is a demultiplexing from a multiple program transportstream into a single program transport, as defined in the MPEG-2specification. This is performed by an MPEG transport chip 54, such asthe 9110B chip commercially available from C-Cube. (A second stagedemultiplexing to separate the video, audio and other data still occursin the set-top electronics, while decoding is preferably only performedat the display terminal or computer.) With this approach, it is notnecessary to send high bandwidth streams throughout the house and theterminals in the home 36 need see only a standardized single programinterface. Compression is required for video generated in the home, e.g.security front door camera or video conference camera.

All the external network interfacing, decryption, access control,demultiplexing to a single program stream, etc., is performed by thenetwork interface module 50. Thus, the network interface module 50buffers the home network hardware and software from the peculiarities ofthe attached external network. Multiple different programs requiremultiple network interface crossbar connections whether from one ormultiple providers. In certain embodiments, a dual module is providedwith two connections to the crossbar, providing two programs receivedfrom the same external network.

The MPEG transport chip 54 performs the MPEG clock recovery and providesthe recovered 27 MHz clock and the selected program to an internalnetwork connection 56. The 27 MHz clock is received by an MPEG tonetwork synthesizer 58 and converted to a 10 MHz clock, for example,when the internal network 34 is a 10base-T Ethernet network. The 10 MHzclock, as well as the selected program, are provided to a conventionaltransceiver 60 (such as an Ethernet transceiver) connected to theinternal network 34. The synthesizer 58 acts to lock the Ethernet clockto the recovered MPEG clock. When the packet of data is transmitted fromthe network interface unit 32 to the set-top electronics 40, the set-topelectronics 40 is locked to the recovered MPEG data at 27 MHz. At theset-top electronics 40, the 27 Mhz clock is regenerated from theEthernet 10 MHz clock by another synthesizer.

The data is received in the set-top electronics 40 by a networkinterface device 62 that includes a network interface 64. The 10 MHzclock recovered by the network interface 64 from the data stream off thenetwork 34 is gated through gate 66 to a network to MPEG synthesizer 68.Gating is needed so that the locking function is performed only whenthere is a packet of data present. The 10 MHz clock is converted to a 27MHz clock provided to an MPEG decoder 70 and a video decoder/encoder 72.The selected program is provided by the network interface 64 to the MPEGdecoder 70, which decodes the MPEG data and provides it to the videodecoder/encoder 72. The data stream is converted by the video encoder 72to a format (e.g., NTSC or SVideo) suitable for use by a display device,such as a television. The video decoder os for the case (HFC) wherethere may be an NTSC analog signal to digitize and merge with on-boardgraphics hardware.

The network 34 in FIG. 4 is depicted schematically, and it should beunderstood from the previous description that the video data may beplaced on the network 34 through the hub 42, but that a direct circuitof the network interface unit 32 and the set-top electronics 40 throughthe direct circuit crossbar 44 of the network 34 is preferred to providea jitter free transfer of video data.

FIG. 5 is a more detailed diagram of an exemplary embodiment of thenetwork interface device 62 of the set-top electronics 40 depicted inFIG. 4. The network interface device 62 includes the network synthesizer68 coupled to a program logic device operating as the gating device 66.The network synthesizer 68 may be implemented by a commerciallyavailable chip, such as the MC145151 manufactured by Motorola. Theprogram logic device 66 may be implemented by a commercially availablechip, such as the MC7958, also manufactured by Motorola. A voltagecontrolled crystal oscillator 80 operates at 27 MHz and provides itssignal to the program logic device 62, which gates the 10 MHz signal tothe synthesizer 68 when there is a received data packet. The synthesizerdivides down the 10 MHz and 27 MHz frequencies to a common frequencywhich is fed into a phase detector of the synthesizer 68. The output ofthe phase detector of the synthesizer 68 is provided as a control signalto the voltage controlled crystal oscillator 80 to adjust the localfrequency up or down to lock to the incoming Ethernet frequency.

The signal informing the program logic device 66 of the receipt of adata packet, and the 10 MHz clock, are provided by a serial interfaceadapter 82 serving as a receive enable. A commercially available productsuitable for the serial interface adapter is Am7992B, manufactured byAdvanced Micro Devices.

The data stream is received through a transformer/filter 84, such as onecommercially available from Pulse Engineering, the PE68026. Collisioninformation is also received through another transformer/filter 86,which can be the same type of transformer/filter as 84. The receiveddata is provided to a first network transceiver 88, such as a twistedpair Ethernet transceiver plus (Am79C100). The output of the firstnetwork transceiver 88 (the received data) is made available to thereceive enable 82 and a controller 90. The controller 90 may be acommercially available product, such as the single-chip Ethernetcontroller Am79C970 (manufactured by Advanced Micro Devices). Thecontroller 90 is coupled to a bus 92, such as a peripheral componentinterconnect (PCI) bus, for providing the received data from the network34 to the MPEG decoder 70 of the set-top electronics 40.

A second network transceiver 92 is coupled to the controller 90, and maybe implemented by the same type of transceiver as 88. The second networktransceiver 92 provides the transmit path for data from the controller90 to the network 34 through the transformer/filter 84.

Collision information is routed through transformer/filter 86 and thesecond transceiver 92 to the controller 90.

FIG. 6 is a more detailed diagram of the internal network connection 56,which has an MPEG to network synthesizer 58 that synthesizes the 10 MHzclock from the 27 MHz MPEG clock recovered by the MPEG transport chip 54(see FIG. 4). A crystal oscillator 96 is coupled to the synthesizer 58to provide a 10 MHz signal. In certain embodiments, the crystaloscillator 96 is a 20 MHz oscillator, and the frequency generated by thesynthesizer is 20 MHz, which is then simply divided to 10 MHz at thereceiver (the set-top electronics 40). A commercially availablesynthesizer is the MC145145-2, manufactured by Motorola.

The 10 MHz clock is provided to a microprocessor interface 98, whichserves as interface for a microprocessor 100. The microprocessorinterface 98, with the microprocessor 100, form the transceiver 60 thatconnects to the internal network 34 through a transformer/filter 102.The microprocessor interface 98 may be, for example, a MC68160 chipmanufactured by Motorola, and the microprocessor may be a MC68EN360,also manufactured by Motorola. The transformer/filter 102 may be thesame type as transformer/filters 84, 86 of FIG. 5.

The separation of the network interface unit 32 from the set-topelectronics 40 provides a number of advantages, as described earlier.The functions (responsibilities) of the conventional set-top boxes withintegrated network interface units are divided in embodiments of thepresent invention. For example, in preferred embodiments, the networkinterface unit 32 is responsible for performing external networkspecific interfacing, tuning demodulation, and error correction. Itprovides external network specific video descrambling andencryption/decryption (credit card number, user password, etc.). Thenetwork interface unit 32 also provides an external network specificprogram guide. Additionally, it performs MPEG transport demultiplexingto a single stream and MPEG reference clock recovery. In preferredembodiments of the invention, the network interface unit provides homenetwork Ethernet interfacing and MPEG/Ethernet clock locking. It alsoprovides the software to support the external network and home networkprotocols for multiple streams and multiple users. The network interfaceunit also has the software to act as the gateway for the home networkand control the buffering of data as necessary.

The set-top electronics 40 essentially acts as an application computerwith audio, video, graphic and analog television interface, in preferredembodiments. For example the set-top electronics provides the homenetwork specific interfacing and data buffering as necessary. Itprovides Ethernet clock/MPEG clock locking in preferred embodiments. Theset-top electronics 40 decodes MPEG video and audio to recover digitalaudio/video. It performs digital to analog conversion for audio andvideo, and supports commands from an infrared remote control. Theset-top electronics 40 provides support for analog video input (NTSC).It interfaces printers, game ports, etc., and supports boot leveloperating system and is able to down load a full system from an externalnetwork. The set-top electronics 40 supports application programs andcommunications through the network interface units to a network providerand program video server.

FIG. 7 is a block diagram depicting in more detail an exemplaryembodiment of the hub 42 and direct circuit crossbar 44 arrangement ofthe present invention and its connection with a network interface unit32 and set-top electronics 40. The direct circuit crossbar 44 and 42selectively provide either a direct circuit between a particular networkinterface unit 32 and a set-top electronics 40, or a simple networkconnection through the hub 42 for these units. In FIG. 7, only portionsof the network interface unit 32 and the set-top electronics 40 aredepicted, for purposes of illustration and explanation.

In preferred embodiments of the present invention, the hub 42 is arelatively simple and inexpensive hub, since it does not include anysort of packet routing switch or store and forward switch. There is nointelligence that examines the traffic and dynamically switches the hubaccording to the transmit and receive addresses as in hubs that havepacket routing switches.

Although only one network interface unit 32 and one set-top electronics40 are shown directly connected in FIG. 7, any number of directlyconnected pairs may be connected by the direct circuit crossbar 44,depending on the size of the crossbar 44. The network interface unit 32and the set-top electronics 40 are each shown with five pin positions orconnections, each of the connections being a pair. This coincides with aconventional telephone plug, the telephone RJ45, which has ten pinpositions.

The internal network 34 provides the connection between the networkinterface units 32, the set-top electronics 40 and the direct circuitcrossbar 44. In preferred embodiments, the internal network 34 is 10 or100base-T Ethernet.

The selection of a network connection or a direct circuit between thenetwork interface unit 32 and the set-top electronics 40 is establishedby a number of switches 108, which are depicted in FIG. 7 with lettersuffixes to distinguish them from each other in the followingdescription. In the example of FIG. 7, the network interface unit 32 andthe set-top electronics 40 are to be directly connected with oneanother, with the network interface unit 32 transmitting data to theset-top electronics 40. A microprocessor 110 serves as the controllerfor the direct circuit crossbar 44 and controls the positions of theswitches 108 in response to user commands that require a direct circuitto perform. For example, a user may choose to watch a movie from a videoon demand service and therefore makes this selection on a hand-heldremote control. The microprocessor 110, in response to this selection,will then change the positions of the switches 108 to establish a directcircuit between the network interface unit 32 that is connected to theexternal network that carries the video on demand service, and theset-top electronics 40 that is coupled to the television receiver onwhich the user desires to view the movie.

In this case, switch 108a is moved to its illustrated position toconnect the transmit lines of transceiver 88 of the network interfaceunit 32 to line 112 of the direct circuit crossbar 44. The transmitlines of transceiver 88 are no longer connected to the network at theTx1 port of the hub 42. Similarly, the receive lines of the transceiver92 of the set-top electronics 40 are connected through switch 108g tothe same line 112 of the direct circuit crossbar 44. With this directcircuit now established, data entering the home through the networkinterface unit 32 is not broadcast over the network via the hub 42, butinstead is provided directly to the set-top electronics 40 at thelocation where the data will be used.

Although the direct circuit established by the direct circuit crossbar44 provides an excellent pathway for data from the network interfaceunit 32 to the set-top electronics 40, it may occur that not all of thedata coming into the network interface unit 32 is meant for the set-topelectronics 40. For example, it is possible that e-mail is received overthis particular network interface unit 32, and the homeowner wantse-mail to be directed to a personal computer, and not to a television.However, there is no connection to the network 34 due to the directcircuit once a direct circuit is established.

To solve this problem, the set-top electronics 40 examines the addressesof the data packets it receives and performs a routing function for datathat is not meant for this set-top electronics 40. The data is re-routedby the set-top electronics 40 onto the network 34 through the hub 42.This re-routing by the end point connection (the set-top electronics 40in this example) avoids the need for the system to use an expensive andcomplicated router. The set-top electronics 40 has a microprocessor 120and associated memory 122 to identify and route the data packets back tothe network 34.

The direct circuit between the network interface unit 32 and the set-topelectronics 40 provides a jitter-free connection for video data, but there-routing of other data into the network 34 through the hub allows morethan one type of data to be carried into the home by the networkinterface unit 32. Once the direct circuit between a network interfaceunit 32 and a set-top electronics unit 40 is established, collisiondetection is required by the set-top electronics 40 to allow it totransmit to the hub 42. The set-top electronics 40 needs to learn ofcollisions and re-transmit the data to the network 34 if such collisionsoccur. The network interface unit 32 can be set, in certain embodiments,to disable collisions because they cannot occur on the direct circuit.However, in certain embodiments, in both the network interface unit portand the set-top electronics port (to the network 34 through the crossbar44), the same collision pair is included for convenience.

In certain preferred embodiments, one of the five pairs of wires isavailable to provide picture-in-picture capability for the system. Forexample, the network interface unit 32 may provide a second stream ofdata through another transceiver 88a over a second pair of transmitwires onto a separate crossbar connection line 114. The set-topelectronics 40, which has another transceiver 88a also connected to line114, receives this second stream of data through the direct circuit toprovide a picture-in-picture on a television screen. Thus, both picturesmay be provided without jitter by separate direct circuits.

In certain preferred embodiments of the present invention, the crossbarswitches 108 are implemented by an analog MOS array of transistors,controlled in response to signals from the controller 110. This isexemplary only, however, as other embodiments employ switches ofdifferent design, as appreciated by one of ordinary skill in the art.

Although the description of the invention depicts the arrangement withcertain logical distinctions of the functionality of various elements,these logical distinctions may be different in other embodiments. Forexample, the hub 42 is described as connected to the internal network.However, the hub 42 may also be logically considered as part of theinternal network, or even forming the network, with the remaining wiringforming means for attaching end terminals to the hub 42. One of ordinaryskill in the art, therefore, will appreciate that the logicaldistinctions depicted and described in the present specification areexemplary only.

The separation of the network interface unit and the set-top electronicsaccording to the present invention provides a relatively inexpensiveconnection of a multitude of devices to each other within the home, andto the outside world.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A direct circuit crossbar and hub arrangement ofa network having end terminals coupled to the network, comprising:adirect circuit crossbar selectively coupled to the end terminals of thenetwork and coupled to the network, the direct circuit crossbarestablishing a direct circuit between two end terminals, and connectingthe two end terminals as a pair to the network; and a passive hub of thenetwork coupled to the end terminals of the network that are notselectively coupled to the direct circuit crossbar and also coupled viathe direct circuit crossbar to the end terminals connected as a pair tothe network.
 2. The arrangement of claim 1, wherein the direct circuitcrossbar has direct circuit lines and controllable switches forconnecting the end terminals to the direct circuit lines.
 3. Thearrangement of claim 2, wherein the direct circuit crossbar has aprocessor responsive to command signals to control the switches toconnect the end terminals to the direct circuit lines, wherein a directcircuit between two end terminals is established by connection of theend terminals to the same direct circuit line.
 4. The arrangement ofclaim 3, wherein the end terminals have receive and transmit lines, andwherein a direct circuit established between two of the end terminalscauses the transmit line of the first one of the end terminals to beconnected to the same direct circuit line as the receive line of thesecond one of the end terminals, the receive line of the first one ofthe end terminals and the transmit line of the second one of the endterminals being connected to the hub.
 5. The arrangement of claim 4,wherein the switches are analog MOS switches.
 6. A method of connectingend terminals to a network, comprising:connecting receive and transmitports of end terminals on a network to a passive hub; selectivelydirectly connecting at least the transmit port of a first one of the endterminals to the receive port of a second one of the end terminals by adirect circuit crossbar to establish a direct circuit between the firstand second end terminals and disconnecting the transmit port of thefirst one of the end terminals from the hub and the receive port of thesecond one of the end terminals from the hub.